Synchronous puffer circuit breaker

ABSTRACT

A high-voltage circuit breaker contains synchronously operated contacts which are opened just prior to current zero. The contacts are contained within a gas-filled vessel and one of the contacts is a nozzle contact. Gas flows through the nozzle contact prior to contact operation, due to the relative movement of a piston and cylinder. The synchronous operating circuit is further constructed to reclose the contacts if current continues to flow between the contacts after they open.

United States Patent Kesselring 451 May 2 1974 [54] SYNCHRONOUS PUFFER CIRCUIT 3,379,850 4/1968 Azinger, Jr 200/l48 J BREAKER 3,390,240 6/l968 Circle et al. 3,551,624 12/1970 Fischer ZOO/I48 A Fritz Kesselring, Kusnacht, Zurich, Switzerland Assignee: Siemens Aktiengesellshaft, Berlin and Munich, Germany Filed: Sept. 5, 1972 Appl. No.: 286,033

Inventor:

Foreign Application Priority Data Sept. 6, l971 Germany 2145071 U.S. Cl. 200/148 A, 200/148 J Int. Cl. H0lh 33/70 Field of Search ZOO/148 J, 148 A References Cited UNITED STATES PATENTS 4/1968 Kesselring 200/148 J Primary Exuminer-Robert S. Macon Attorney, Agent. or Firm-Ostrolenk, Faber, Gerb &

Soffen [57] ABSTRACT A high-voltage circuit breaker contains synchronously operated contacts which are opened just prior to current zero. The contacts are contained within a gasfilled vessel and one of the contacts is a nozzle contact. Gas flows through the nozzle contact prior to contact operation, due to the relative movement of a 1 piston and cylinder. The synchronous operating circuit is further constructed to reclose the contacts if current continues to flow between the contacts after they open.

6 Claims, 8 Drawing Figures Z i a Z Z I. 1

ATENTEDMM 28 mm SHkEI 1 (IF 4 PATENTEBmza 1524 3813507 SHEET 3 OF 4 HUI! BACKGROUND OF THE INVENTION This invention relates to high-voltage circuit breakers, and more particularly relates to a novel combination of a synchronously operated pair of contacts and a puffer-type breaker to produce an improved circuit interrupting device.

Synchronous circuit breakers are well known to the art, and generally consist ofa pair of relatively movable contacts which can be opened immediately prior to a current zero. By operating the contacts at this time, the circuit breaker need not have substantial arc interruption capacity or contain arc interruption auxiliary equipment, so that the size of the breaker can be reduced for a given application. Such breakers may also be contained within an atmosphere of sulfur hexafluoride, which may be used to enhance any necessary interrupting capability for the breaker, andto insure the dielectric integrity of the gap between the contacts.

after the contacts have opened.

In the event that a synchronous circuit breaker fails to clear a fault current for any reason,'the breaker can be seriously damaged by the flow of fault current since it has limited interrupting capacity. Consequently, it is well known to automatically reclose synchronous circuit breakers, if the main circuit current is not interrupted at the current zero. Thus, the contacts are immediately reclosed and circuit interruption is again attempted prior to the next current zero. A snychronous circuit interrupter with this reclosing function upon an unsuccessful interruption is shown in US. Pat. No. 3,449,537, in the name of Kesselring, entitled CIR- CUIT BREAKER FOR INTERRUPTING AT ZERO CURRENT AND AUTOMATICALLY RECLOSING AFTER UNSUCCESSFUL INTERRUPTION.

Circuit interrupters are aslo known in which are current interruption is obtained by forcing a blast of air or other gas through the separating contacts and through the arc drawn between them.

Gas pressure for forcing gas through a contact nozzle can be obtained by providing two separate pressure systems, as in US. Pat. No. 3,6l4,3 57, in the name of Jensen, entitled GAS BLAST CIRCUIT INTERRUPT- ER USING MAIN MOVABLE CONTACT AS BLAST VALVE, wherein gas flows from the highpressure section of the breaker through the separating contacts and into the low-pressure section of the breaker during the time that the contacts are opening and during the time that arcing occurs. This gas may be sulfur hexafluoride which has exceptional arc interruption qualities andwhich also provides gq' ia dielectric qualities for insulating the open contact pressure source, but produces high pressure by the movement of a piston relative to a cylinder at the time the contacts are operated. Putter-type interrupters using sulfur hexafluoride as the interrupting medium are shown, for example, in US. Pat. No. 2,933,575,

dated Apr. 19, 1960. entitled CIRCUIT INTERRUP'F Pufi'er breakers generally exhibit large contact nozzle cross-sections through which the generated gas must move when interrupting an-arc. Moreover, considerable back pressure is developed during the interruption operation, and the breaker contacts will exhibit burning due to arcing and gas decomposition during arcing.

BRIEF SUMMARY OF THE INVENTION suitable arc interruption gas at positive pressure for example, l0 atmospheres. The interrupting gas may be a pure electro-negative gas such as sulfur hexafluoride, either by itself or mixed with other gases such as nitrogen gas.

The interrupter units are supported within this grounded housing and contain a piston movable relative to a cylinder, wherein the circuit breaker operating mechanism initially moves a piston within a cylinder in order to produce gas movement or increase gas pressure adjacent the cooperating contacts. A synchronous operating mechanism actually separates the contacts immediately prior to current zero and in the presence of the gas blast created by the puffer mechanism. Thus, the interrupting capacity which is required by the novel interrupter of the invention will be about 1 percent of an equivalent asynchronous interrupter. Consequently, the decomposition of the arc quenching gas and the burning of the contacts will be minimized, so that the puffer-type mechanism is most advantageously used in the combination.

By selecting a suitable high gas pressure within the BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-sectional view taken through a circuit breaker constructed in accordance with the principles of the present invention.

FIG. 2 illustrates the manner in which the circuit breaker of FIG. 1 is modified for mounting in a gasinsulated transmission system.

FIG. 3 is a further modification of the circuit breaker arrangement of FIG. 1 illustrating the series connection of four interrupter units to increase the voltage capability of the device.

FIG. 4 is a cross-sectional view of the electrodynamic operating mechanism used in connection with the circuit breaker of FlG. 1.

FIG. 5 is a cross-sectional view of a modification of the electrodynamic drive mechanism of FIG. 4.

FIG. 6 is a circuit diagram of the operating circuit for the electrodynamic mechanism of FIGS. 4 and 5.

FIGS. 7 and 8 are diagrams illustrating the operation of the circuit of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a grounded spherical housing consisting of lower body 1 which has an upper cap 2. Members 1 and 2 are made of a nonmagnetic material such as a suitable aluminum alloy. The tank formed by members 1 and 2 is circular in cross-section but may have any other desired shape. The width of the tank, for example, can be foreshortened (not shown) so that the overall tank shape would be disk-like.

Two terminal bushing conductors 3 enter the upper cap 2 and are supported by insulation tubes 4, which are sealed relative to cap 2 within the flanges 5. Note that any desired terminal bushing structure can be used and the terminal bushing of FIG. 1 is only schematically illustrated. Suitable current transformers 28 can surround flanges 5.

The grounded tank is preferably mounted in such a manner that the lower body 1 can be lowered relative to a fixedly supportd cap 2. In this manner, all of the essential components of the circuit breaker can be exposed for maintenance or repair simply by lowering body 1 without having to interfere with the circuit breaker internal assembly or the connection of the circuit breaker terminals to the external circuit.

Two identical series-connected interrupter structures 7 are contained within the tank and are supported from cap 2. Thus, the interrupters contain, as shown for the case of the left-hand interrupter structure 7, a conductive stationary contact nozzle 8 which extends into an expanding discharge end or elbow 9, which discharges into the main volume within the tank. The conductive nozzle 8 and its discharge elbow 9 are electrically connected to the ends of the terminal bushing stud 3 and may be an integral part of the casting which forms the stud 3.

An arcing contact 10 is provided, which is relatively movable into and out of contact with the nozzle end of stationary contact 8. Arcing contact 10 is shown in the engaged position in FIG. I.

The interrupter 7 further contains a main movable contact which is schematically shown in FIG. 1 as a spreading-type contact arrangement which consists of a plurality of contact fingers 11 which are pivotally mounted at their bottom and which are surrounded by a pressure spring Ila. An operating disk 12 is then contained within the center of the cluster of contact fingers 11 and above the level of spring 11a. Spreading disk 12 is also directly connected to arcing contact 10.

As will be seen hereinafter, when spreading disk 12 moves downwardly, it presses the individual contact fingers 11 away from one another since they tend to pivot about their lower support ends, thereby to causev the individual contact fingers to radially separate from the outer peripheral end of nozzle 8. At the same time, the arcing contact 10 moves straight down and out of engagement with the end of nozzle 8. An insulation cylinder 13 which is supported by the member 9 and is sealed relative thereto encloses the upper part of nozzle 4 8 and the upper portion of the main contacts 11. The

bottom of cylinder 13 is received by the conductive plate 14, which also contains a circular depression therein for receiving the bottom ends of the contact fingers forming the main movable contact 11 which is spread to a disengaged position by the spreading disk 12.

' A second insulation cylinder portion 15 is positioned beneath plate 14 and is sealed relative thereto, with the members 13, 14 and 15 all being supported from the terminal bushing member 4. An operating piston 16 is then disposed within cylinder 15 and a conical spring 17 is disposed between the top of piston 16 and the bottom of plate 14 to bias piston 16 downwardly.

The conductive plate 14 is provided with suitable openings, such as opening 14a, shown in FIG. 1, which permits are quenching gas to flow from the chamber between piston 16 and the bottom of plate, 14 when the piston 16 is moved upwardly. Gas flowing through port 14a will then increase the pressure within cylinder 13, so that thus gas can flow from chamber 13 into nozzle 8 and out through elbow 9 and into the main tank body.

The operating mechanism for operating the spreading disk 12 which, in turn, causes the opening of contacts 11 and the disconnection of arcing contact 10, includes the lever 18 which is pivoted at fixed pivot 18a, and which has its left-hand end connected to the disk 12 by means of a suitable link. The righthand end of lever 18 is connected to an operating tube 19 which is, in turn, operated by an electrodynamic drive system 20.

Piston 16 of the puffer portion of the breaker is connected, by rod 21 and crossbar 22, to an operating lift rod 23. The operating lift rod 23 is then terminated at its upper end by a piston 24 which moves within cylinder 25 which is suitably mounted from cap 2. Note that the electrodynamic drive of mechanism 20 is also contained in the same housing which is supported by cap 2.

The interior of cyliner 25 can be connected to ambient low pressure by opening valve 27. Normally, the interior of the cylinder will be at the pressure of the main tank since gas can fill cylinder 25 through openings 24a in piston 24.

The interior of the sealed housing consisting of components 1 and 2 is filled with a suitable mixture of sulfur hexafluoride and nitrogen gas under a positive pressure of about 10 atmospheres. Note that the housing is permanently sealed, so that the gas is always contained within the housing, and the housing need not be filled or held under pressure by a constantly operating compressor. If desired, however, suitable fixtures can be connected to the housing to allow for the periodic removal of the gas therein, for cleaning, or the like.

The synchronous operating mechanism 20, as shown in FIG. 1, consists of stationarily mounted drive coils 20a and 2012 which are selectively energized upon the actuation of a suitable energizing circuit. A conductive disk 200, which acts as a short-circuited winding, is then fixed to the top of operating tube 19, so that the disk 20c will be repelled from the coil to which it is closely coupled, whether coil 20a or 20b, when these coils are energized.

It was pointed out previously that both interrupters 7 are identical in construction. The two interrupters of FIG. 1 are connected in series through the conductive plate 14, so that there are two breaking gaps in series provided for the circuit breaker. Additional series interrupting gaps can also be provided, as will be shown hereinafter in connection with the circuit breaker of FIG. 3.

The operation of the arrangement shown in FIG. 1 is as follows:

The circuit breaker is shown in FIG. 1 in its closed position and a current path is formed between the terminal bushing studs 3 through the conductive members 9, the stationary nozzle contacts 8, the main contacts 11 and the conductive plate 14. Note that in FIG. 1 and with the breaker in the closed position that the operating tube 19 is in its lower-most position, with member 200 seated directly atop impulse winding 20a. Thus, the lever 18 is rotated in its most clockwise position and the spreading disk 12 is in its upper-most position to enable the contact fingers 11 to be pressed against the stationary nozzle contact 8 by the spring 11a. At the same time, .the arcing contact is pressed into the nozzle opening in the nozzle 8, as shown.

In oreder to open the circuit breaker, a suitable operating circuit and mechanism, which responds to either a manual or automatic circuit breaker opening signal, first causes the opening of valve 27. The cylinder 25 was filled with SE, at the pressure of the gas within lower body 1 and cap 2 (by leakage through opening 24a) and the opening of valve 27 causes this relatively small gas volume to be released to the external atmosphere. The gas pressure beneath piston 24 (IO atmospheres) then moves piston 24 and lift rod 23 (which is slidably movable relative to tube 19) upwardly with relatively high force. The upward movement of lift bar 23 causes the crossbar 22 to move upwardly, thereby to move piston operating shafts 21 and pistons 16 upwardly against the biasing force of springs 17. The upward movement of pistons 16 compresses the gas atop the pistons 16 and this compressed gas is driven through openings 14a in plate 14 and through the noz-- zle-shaped stationary contacts 8 into and exteriorly of insulation cylinder 13 through the elbows 9.

The gas velocity through the nozzle 8 at full nozzle opening depends upon the cross-section of the nozzle opening relative to the cross-section of piston 16 and the velocity of piston 16. With these parameters, a flow velocity of about 100 meters per second can be produced without difficulty, where this fow velocity is extremely advantageous for an arc quenching function.

After the pistons 16 have moved upwardly to compress gas and to begin the movement of gas through nozzle 8, an impulse circuit, which will be described hereinafter in connection with FIGS. 6, 7 and 8, operates to provide a strong pulse current in coil a. As is well knownfor electrodynamic drive systems, a circulating current will be induced in conductive disk 20c,

, so that the disk 20c will be strongly repelled from winding 20a.

By producing the current impulse in winding 20a just prior to a current zero, the tube 19 will begin to move upwardly just prior to the current zero so that the interrupter contacts will open immediately prior to zero current passage and, presumably, can open without arcing. That is, the upward movement of rod 19 causes the counterclockwise movement of lever 18 which moves spreading disk 12 downwardly. This causes the spreading movement of contact fingers 11, thereby to disconnect them from nozzle 8 against the biasing force of spring 11c, and further moves the arcing contact 10 away from the stationary contact 8. Thus,'an arc is drawn between members 8 and 10, but, since this occurs immediately prior to current zero, the arc should extinguish without excessive burning of the contacts and without excessive gas decomposition. Note that this relatively small amount of arcing will be adequately dealt with by the flow of gas produced by the movement of piston 16 just prior to the opening of the contacts. A suitable latching mechanism is then provided to hold the contacts open until a reclosing signal is generated.

Once the contacts are opened and the arcs are successfully quenched, valve 27 is closed so, that gas can flow through the port 240 in piston 24 so that pressure equalizes on both sides of piston 24. The springs 17, bearing on piston 16, are then able to move the crossbar 22 and lift rod 23 downwardly to return the pistons 16 to the position shown in FIG. 1.

In order to close the circuit breaker, when the interrupter contacts are open and the crossbar 22 is in its downward position, the pulsing circuit of the electrodynamic drive system, which will be hereinafter described, is excited to apply a current pulse to coil 20b. The coil 20b is closely coupled at this time to disk 200 so that a downward accelerating force is applied to disk 20c, whereupon the disk 19 moves downwardly and the spreading disk 12 moves upwardly to permit closing of contacts 10 and 11 relative to nozzle contact 8. Note that no gas flow occurs during the closing of the interrupters. The circuit closing arc, however, is extremely short because of the high speed closing of the device.

' zero, then the electrodynamic operating mechanism is re-energized to apply a pulse to coil 20b which initiates immediate reclosing of the circuit interrupter. Thus, as will be seen more fully hereinafter in connection with FIGS. 6 to 8, if the circuit interrupter is opened and disk 20c reaches coil 2012, so that the contacts 10 and 11 are separated from contact 8 and if, under this situation, arc current continues to flow between the opened contacts (indicating an unsuccessful synchronous opening) then a current pulse will be applied to coil 20b to close the interrupter contacts. The electrodynamic drive circuit will then attempt to open the interrupter prior to the next current zero.

Note that in the subsequent current zero operation following an unsuccessful interruption, the pressure at nozzle 8 and gas flow through nozzle 8 are greater than the initial interrupting pressure and gas flow since the piston 16 has continued to move upward and continued to compress gas during the interval in question. Thus, there is an improved likelihood that there will be a successful subsequent interruption of the arc during subsequent current zero interruption operations following an unsuccessful interruption operation.

One specific embodiment for the electrodynamic drive mechanism of FIG. 1 is shown in FIG. 4. In FIG. 4, components similar to those of FIG. 1 have been given similar identifying numerals. Thus, the mechanism 20 includes coils 20a and 20b which are stationarily mounted in respective insulation housings 51 and 52, respectively. Terminals 54 and 55 extend through insulation housing 51 and are the terminals for winding 200. Similarly, terminals 57 and 58 extend through the insulation housing portion 52 and are the terminals for winding 20b. FIG. 4 also illustrates the lift rod 23 which is slidably movable relative to contact operating tube 19. Note that tube 19 is sealed relative to housing 51 by the seal 64.

The conductive disk 200 is a disk of any good conducting and mechanically strong material such as a copper manganese alloy and is firmly attached to the tube 19. The entire assembly illustrated in FIG. 4 is suitably mounted within the insulation cylinder 26, shown in dotted lines in outline, and the volume between windings 200 and 20b is filled with a suitable damping fluid 61 which operates to damp the movement of disk 200 during itsoperation. A channel 62 is formed in the insulation body 52 so that the damping fluid can overflow above the top of insulation body 52 to the level indicated to accommodate expansion and contraction of the damping fluid volume due to temperature changes, and the like. The upper insulation housing 52 is further provided with a disk-shaped depression 65 which serves to finally damp the upward movement of disk 20c.

In operation, when the mechanism 20 is in the position shown in FIG. 4, the interrupter contacts will be closed. In order to open the contacts, coil 20a is excited so that the disk 200 is rapidly accelerated upwardly and away from coil 20a. The motion of the disk 200 is loosely damped by the fluid 61 since the disk 20c can move fairly easily through the fluid 61 during its initial motion. However, once the disk 20c disk-shaped space 65, a more intense damping occurs since there is a fairly good fit of the disk 20c within opening 65, thereby producing heavy damping of the upward motion of disk 206. It can be shown that, if the moving mass associated with disk 200 is about 0.6 kilograms and moves at a speed of about 8 meters per second, it is possible to decelerate the movement of the disk 20c over a distance of about 2 millimeters within the confines of the disk-shaped opening 65. Once the disk 20c seats within the opening 65, the interrupter contacts will be fully open and may be latched open by any suitable means desired, which latch will be defeated upon the actuation of coil 20h which drives the disk 20c down.

FIG. shows a modified design for the electrodynamic drive mechanism of FIG. 4 in which improved initial movement of conductive disk 200 is obtained upon the energization of coil 20a. In FIG. 5 all components similar to those of FIG. 4 have been given the same identifying numerals. The parts have been slightly modified, however, so that a cage-type spacer 66 is contained within the fluid volume 61. The cage-type spacer 66 consists of piston members 66a and 66!) which move respectively into disk-shaped volumes 65a and 65, respectively, in insulation supports 51 and 52, respectively, with piston members 66a and 66b rigidly connected together by joining bars 67.

In the embodiment of FIG. 5, it will also be noted that the conductive disk 200 has a somewhat smaller diameter than in FIG. 4, and that its peripheral edge is rounded. Thus, the disk can initially move with relatively little resistance through the fluid 61 until its upper surface reaches the inside surface of piston member 66a. Once disk 20c engages the bottom of piston 660, it causes the entire cage 66 to move upwardly, with the bottom surface of piston 66 moving out of cav ity 65a and the upper surface of piston 66a moving into cavity 65. Thus, the disk 20c will initially move with-extremely high acceleration, but, once it reaches its limiting position, there is a double decelerating force applied to the disk 20c through the pistons 66a and 66b which move relative to confined cavities 65 and 65a, respectively.

FIG. 2 shows an embodiment of the invention where the circuit breaker can be mounted in a gas-insulated transmission system. In FIG. 2, substantially the same components described in connection with the circuit breaker of FIG. 1 are used and have been given similar identifying numerals. The terminal construction is changed, however, and the housing construction consists of housing portions 38a and 38b which are bolted together thereby where the lower portion 38a contains flanges 34. The flanges 34 then receive transmission line conductors 31 which are supported by insulation v bushings 4, as shown, and which are connected to the central conductors of a conventional gas-insulated transmission system. Thus,.the conventional portion of the system includes an outer tubular grounded housing 33 which contains a plurality of spaced disk insulators 32 which support the extending elongated control conductors.

FIG. 3 illustrates a further embodiment of the invention in which the circuit breaker has four breaks in series rather than two breaks in series, as in FIGS. 1 and 2. Thus, in FIG. 3 there are two separate breaker assemblies la and 1b, which are essentially similar to the construction of FIG. 1, except that the tank tops each have provision for only a single terminal bushing. In addition, the tank bottoms are provided with terminal bushings 4a and 412, respectively, which contain conductors which are connected in series with one another, and are further connected to one of the tank interrupters through a conductive spring connection 44. The two main terminals of the assemblage may then be connected to gas-filled conductors 41 of a gas-insulated transmission system line.

FIGS. 6, 7 and 8 illustrate the details of the construction and operation of a synchronous operating circuit which can be used to produce pulses for the electrodynamic drive mechanism 20. Thus, FIG. 6 schematically illustrates conductive disk 20c movable between stationary coils 20a and 20b.

The circuit of FIG. 6 further contains a central circuit conductor which passes through a magnetic core 71 and which carries a current which is the main current to be interrupted and which flows through the interrupters 7 of the preceding figures. The core 71 is magnetically coupled to the conductor carrying the current i, to form a current transformer 78.

The core 71 is provided with air gaps, for example, two gaps 71a and 71b of about 0.1 millimeters each. The current 1', through core 71 creates a magnetic field intensity H shown in dot-dash lines in FIG. 6, and further creates a magnetic field intensity H in core 71. The magnetic field H is coupled to the iron core consisting of U-shaped pole-piece 72 and a magnetically saturable leg 73 extending across the poles of the U- shaped member 72.

Pole-piece 72 has a winding 74 thereon which is connected in series with a capacitor 75 and a winding 76 on saturable member 73. An induced current i will flow in the winding 74 due to the field H and the ampere turns of the winding 76 will oppose the ampere of winding 76) where these ampere turns lead the ampere turns i,N,of the current transformer 78. The flux in core portion 36 will then execute the flux change shown as 0,, in dotted lines in FIG. 7, to produce an output voltage u in the winding 77 just prior to the time that the ampere turns i,,l l pass through zero.

It should be noted that the production of a synchronous current pulse in the manner described above in connection with FIGS. 6 and 7 is similar in nature to the system described, for example, in German Pat. No. 1,463,586.

In order to produce a further operating pulse which can be connected to winding 20b in the event of an unsuccessful synchronous interruption, circuitry is provided for monitoring continued current flow i after an attempted interruption. This circuitry includes the winding 80 on core 71, the output of which is connected to a single-phase, full-wave, bridge-connected rectifier 81. The output of rectifier 81 is then connected to the primary winding 82 of a core 83 which has an air gap therein to prevent its saturation.

A secondary winding 84 then has an output voltage produced thereon in the manner described in connection with FIG. 8. Thus, the current i, of FIG. 8 is the output current of rectifier 81. The flux shown in dotted lines, is the magnetic flux in core 83 due to the current i where this flux produces a positive output voltage u prior to zero instantaneous current for the current I, and a negative voltage a, immediately after the zero current 4i Note that the output winding 84 is connected in series with a diode 85 which blocks the positive output voltage u, but permits passage or con ducts the current produced by negative output voltage The manner in which the output pulses of winding 77 and of winding 84 are processed in order to control the electrodynamic drive system is further illustrated in FIG. 6. Thus, winding 77 and winding 84 are connected to amplifiers 86 and 87 respectively which are, in turn, connected to the trigger electrodes 91 and 92 of spark gap 90. The spark gap 90 is then connected in series with switching condensers 88 and 89 which may be suitably charged from any desired type source (not shown), so that these condensers will be selectively discharged into coils 20a and 201) respectively upon the ignition of spark gap 90. Note that spark gap 90 could be replaced by any desired type of switching device, such as a thyristor.

There is further provided a circuit arming switch 93 which can be manuallyoperated or operated by any desired overload protection circuit in order to allow discharge of the capacitor 88 into the operating coil 20a at an appropriate time.

There is further provided, in the embodiment of FIG. 6, a switch actuating extension 100 carried on the movable disk 20c, where the member 100 cooperates with spring-biased switches 98 and 99. Thus, switches 98 and 99 are normally spring-biased open. However, when the disk 200 is in the lower position above, it

presses switch 98 closed, while, if the disk 20c is in the upper position shown in dotted lines, it will permit switch 98 to open and cause switch 99 to close. Thus, condensers 88 and 89 will discharge into either coil 200 or 20b, respectively, with the triggering of the spark gap depending on the closure of switches 99 and 98 respectively.

In operation, assuming that the circuit breaker is closed, the conductive disk 20c is in the position shown in FIG. 6. If it is now desired to synchronously open the breaker, the circuit of FIG. 6 is suitably activated by closing switch 93 so that at some time prior to a zero instantaneous current for the current i an output pulse is produced in winding 77 which is amplified by amplifier 86 to produce a firing signal on trigger electrode 91 to fire spark gap 90. The firing of gap 90 then permits capacitor 88 to discharge through spark gap 90, coil 20a, switch 98 and switch 93. This then causes a rapid acceleration of the conductive disk 20c upwardly to open the breaker at a current zero. Note that the upward movement of disk 20c permits the opening of switch 98 which cuts off the discharge current from capacitor 88 and to extinguish spark gap 90.

If the current i, is successfully interrupted at this time, then the current i, of FIG. 8 will extinguish and the reconnection impulse u, is not produced. However, it the current i continues to flow, the voltage 1', is produced and is amplified by amplifier 87 to cause the reignition of spark gap 90. Note that the spring contact 99 has been closed by the extension member 100 of disk 20c which is now moved toward the dottedline position in FIG. 6.

Capacitor 89 will then discharge through spark gap 90, coil 20b and switch 99, thereby to induce a rapid reclosing movement of the disk 20c, moving it downwardly to the contact closed position. This opens contact 99 so that spark gap 90 is extinguished and ultimately closes contact 98 so that the circuit is in condition to produce a new synchronous opening operation prior to the next current zero.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

l. A circuit interrupter comprising, in combination:

a pair of cooperable contacts movable between an engaged and disengaged position;

a synchronous operating mechanism connected to at least one of said pair of cooperable contacts for moving said pair of cooperable contacts to said disengaged positionjust prior to a current zero instant for current flow through said pair of cooperable contacts;

a gas puffer comprising a gas-filled cylinder and a relatively movable piston therein; said pair of cooperable contacts positioned relative to said gas-filled cylinder such that gas, due to the relative movement of said cylinder and said piston, flows through arcs drawn between said pair of cooperable contacts when said contacts are moved to their disengaged position;

and an operating mechanism for moving said piston and said cylinder relative to one another; said operating mechanism operating jointly with said synchronous operating mechanism, whereby gas moves through said pair of contacts at least during the time said contacts are moved to their said disengaged position.

2. The circuit interrupter of claim 1 which further includes reclosing mechanism connected to said pair of cooperable contacts and to the circuit containing said pair of contacts for reclosing said contacts after they are moved to their said disengaged position if current flows between said contacts after said instantaneous current zero.

3. The circuit interrupter of claim 1, wherein said synchronous operating mechanism includes an electrodynamic system.

4. The circuit interrupter of claim 1 which includes a gas-filled grounded conductive housing; said pair of cooperable contacts and said gas puffer being contained within the interior of said grounded conductive housing.

5. The circuit interrupter of claim 1 which includes a gas-filled grounded conductive housing; said pair of cooperable contacts and said gas puffer being contained within the interior of said grounded conductive housing; said housing being filled with gas which at least includes SF said gas being at a positive pressure above ambient pressure.

6. The circuit interrupter of claim 5 which further includes reclosing mechanism connected to said pair of cooperable contacts and to the circuit containing said pair of contacts for reclosing said contacts after they are moved to their said disengaged position if current flows between said contacts after said instantaneous current ZCl'O. 

1. A circuit interrupter comprising, in combination: a pair of cooperable contacts movable between an engaged and disengaged position; a synchronous operating mechanism connected to at least one of said pair of cooperable contacts for moving said pair of cooperable contacts to said disengaged position just prior to a current zero instant for current flow through said pair of cooperable contacts; a gas puffer comprising a gas-filled cylinder and a relatively movable piston therein; said pair of cooperable contacts positioned relative to said gas-filled cylinder such that gas, due to the relative movement of said cylinder and said piston, flows through arcs drawn between said pair of cooperable contacts when said contacts are moved to their disengaged position; and an operating mechanism for moving said piston and said cylinder relative to one another; said operating mechanism operating jointly with said synchronous operating mechanism, whereby gas moves through said pair of contacts at least during the time said contacts are moved to their said disengaged position.
 2. The circuit interrupter of claim 1 which further Includes reclosing mechanism connected to said pair of cooperable contacts and to the circuit containing said pair of contacts for reclosing said contacts after they are moved to their said disengaged position if current flows between said contacts after said instantaneous current zero.
 3. The circuit interrupter of claim 1, wherein said synchronous operating mechanism includes an electrodynamic system.
 4. The circuit interrupter of claim 1 which includes a gas-filled grounded conductive housing; said pair of cooperable contacts and said gas puffer being contained within the interior of said grounded conductive housing.
 5. The circuit interrupter of claim 1 which includes a gas-filled grounded conductive housing; said pair of cooperable contacts and said gas puffer being contained within the interior of said grounded conductive housing; said housing being filled with gas which at least includes SF6; said gas being at a positive pressure above ambient pressure.
 6. The circuit interrupter of claim 5 which further includes reclosing mechanism connected to said pair of cooperable contacts and to the circuit containing said pair of contacts for reclosing said contacts after they are moved to their said disengaged position if current flows between said contacts after said instantaneous current zero. 